The effect of sowing time on Alternaria brassicae and Phyllotreta Spp. spreading in spring oilseed rape crop

Abstract

The field experiments were conducted at the Experimental Station of Aleksandras Stulginskis University in 2016-2017. The aim of the experiment was to evaluate the influence of sowing time on spreading of pests and diseases in spring oilseed rape crop. The first sowing occurred when soil reached physical maturity, the other sowing dates were every 5 days in 2016 and every 7 days in 2017. In 2016-2017, the rape seedlings in the plots of the latest sowing were significantly more damaged compared with those of earlier sowing dates. In 2016-2017, Phyllotreta spp. was more intensively spread in the crops sown in April, and rape seedlings were significantly more damaged. In 2016, there was a very strong statistically significant correlation between the sum of positive temperatures for the 10-day period up to the sowing of rapeseed and the prevalence of Phyllotreta spp. in crops: r = 0.98, P < 0.05, and the damage intensity of rape seedlings by Phyllotreta spp. of (BBCH 10-19): r = 0.92, P < 0.05. The warmer the weather was before rape sowing, the more active Phyllotreta spp. was. In 2017, strong correlations were established between the number of Phyllotreta spp. and the intensity of crop damage by Phyllotreta spp. and the crop density 3 days after the emergence: r = -0.82, P < 0.05; r = -0.89, P < 0.01, and 7 days after the emergence of spring rape: r = -0.81, P < 0.05; r = -0.88, P < 0.01.